Base station and method of handling secondary cell group configuration in secondary node change

ABSTRACT

A first base station is configured to execute instructions of the first BS receiving a first interface message for a communication device from a second BS; the first BS transmitting a second interface message to the second BS in response to the first interface message, wherein the second interface message comprises a secondary cell group configuration and an information element causing the first BS to comprise an indication indicating release of SCG in a radio resource control message; and the first BS transmitting the RRC message to the communication device, wherein the RRC message comprises the SCG configuration and the indication.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. application Ser.No. 16/001,961, filed on Jun. 7, 2018. The U.S. application Ser. No.16/001,961 claims the benefits of U.S. Provisional Application No.62/516,662 filed on Jun. 7, 2017, and U.S. Provisional Application No.62/520,575 filed on Jun. 16, 2017, U.S. Provisional Application No.62/570,644 filed on Oct. 10, 2017, and U.S. Provisional Application No.62/660,260 filed on Apr. 20, 2018, which are incorporated herein byreference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a base station and a method used in awireless communication system, and more particularly, to a base stationand a method of handling a secondary cell group configuration in asecondary node change.

2. Description of the Prior Art

In 3rd Generation Partnership Project (3GPP), a next generation cellularsystem called a new radio (NR) system or a fifth generation (5G) systemis recently developed.

SUMMARY OF THE INVENTION

The present invention therefore provides a method and relatedcommunication device for handling a secondary cell group configurationin a secondary node change.

A first base station (BS) comprises at least one storage device, and atleast one processing circuit, coupled to the at least one storagedevice. The at least one storage device stores, and the at least oneprocessing circuit is configured to execute instructions of: the firstBS receiving a first interface message for a communication device from asecond BS; the first BS transmitting a second interface message to thesecond BS in response to the first interface message, wherein the secondinterface message comprises a secondary cell group (SCG) configurationand an information element (IE) causing the first BS to comprise anindication indicating release of SCG in a radio resource control (RRC)message; and the first BS transmitting the RRC message to thecommunication device, wherein the RRC message comprises the SCGconfiguration and the indication.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a wireless communication systemaccording to an example of the present invention.

FIG. 2 is a schematic diagram of a communication device according to anexample of the present invention.

FIG. 3 is a flowchart of a process according to an example of thepresent invention.

FIG. 4 is a flowchart of a process according to an example of thepresent invention.

FIG. 5 is a flowchart of a process according to an example of thepresent invention.

FIG. 6 is a flowchart of a process according to an example of thepresent invention.

FIG. 7 is a flowchart of a process according to an example of thepresent invention.

DETAILED DESCRIPTION

FIG. 1 is a schematic diagram of a wireless communication system 10according to an example of the present invention. The wirelesscommunication system 10 is briefly composed of a communication device100, a base station (BS) 102 and a BS 104. In FIG. 1, the communicationdevice 100, the BS 102 and the BS 104 are simply utilized forillustrating the structure of the wireless communication system 10.

As shown in FIG. 1, the communication device 100 may be configured tosimultaneously connect to the BSs 102 and 104 (i.e., dual connectivity(DC)). That is, the communication device 100 in the DC may perform atransmission/reception via both the BSs 102 and 104. For example, thecommunication device 100 may receive packets from the BS 102 at a firstcarrier frequency and the BS 104 at a second carrier frequency, or thecommunication device 100 may transmit packets to the BS 102 at a firstcarrier frequency and the BS 104 at a second carrier frequency. Inaddition, one of the BSs 102 and 104 may be a master node (MN) and theother BS may be a secondary node (SN). The first carrier frequency andthe second carrier frequency may or may not be overlapped.

The communication device 100 may be a user equipment (UE), a mobilephone, a laptop, a tablet computer, an electronic book, a portablecomputer system, a vehicle or an airplane. In addition, for an uplink(UL), the communication device 100 is a transmitter and the BS(s) 102and/or 104 is a receiver(s), and for a downlink (DL), the BS(s) 102and/or 104 is a transmitter(s) and the communication device 100 is areceiver.

FIG. 2 is a schematic diagram of a communication device 20 according toan example of the present invention. The communication device 20 may bethe communication device 100, the BS(s) 102 and/or 104 shown in FIG. 1,but is not limited herein. The communication device 20 may include atleast one processing circuit 200 such as a microprocessor or ApplicationSpecific Integrated Circuit (ASIC), at least one storage device 210 andat least one communication interfacing device 220. The at least onestorage device 210 may be any data storage device that may store programcodes 214, accessed and executed by the at least one processing circuit200. Examples of the at least one storage device 210 include but are notlimited to a subscriber identity module (SIM), read-only memory (ROM),flash memory, random-access memory (RAM), hard disk, optical datastorage device, non-volatile storage device, non-transitorycomputer-readable medium (e.g., tangible media), etc. The at least onecommunication interfacing device 220 is preferably at least onetransceiver and is used to transmit and receive signals (e.g., data,messages and/or packets) according to processing results of the at leastone processing circuit 200.

In the following examples, a UE is used for representing thecommunication device 100 in FIG. 1, to simplify the illustration of theembodiments.

There are two cases that a delta configuration cannot be performed in achange of SN procedure (e.g., a SN for the UE is changed from a sourceSN to a target SN) which may be initiated by a MN or by the source SN.One case is that a target SN may not comprehend a configurationconfigured by a source SN. The target SN may reject a SN AdditionRequest message received from the MN in this case. The other case isthat the source SN and the target SN may not belong to the same vendor.The target SN does not want to reuse any configuration configured by thesource SN but has no means to perform a full configuration. In thiscase, the target SN may also reject the SN Addition Request message. Inthe both cases, the MN may need to configure the UE to release asecondary cell group (SCG). That is, the UE is not configured in DCanymore and is only configured to connect to the MN, i.e. only theconnection with the MN is kept.

A process 30 in FIG. 3 may be utilized in a UE, and includes thefollowing steps:

Step 300: Start.

Step 302: The UE communicates with a first BS according to (e.g., using)a master cell group (MCG) configuration and communicates with a secondBS according to a first SCG configuration when the UE is in the DC withthe first BS and the second BS.

Step 304: The UE receives a first radio resource control (RRC) messagefrom the first BS.

Step 306: The UE releases the first SCG configuration according to anindication indicating release of SCG (e.g., SCG release or SN release)and communicates with a third BS according to a second SCGconfiguration, when the first RRC message comprises the second SCGconfiguration and the indication.

Step 308: End.

In one example, the UE keeps (e.g., maintains or does not release) atleast one configuration of a plurality of configurations comprised inthe first SCG configuration and communicates with the third BS accordingto the at least one configuration and the second SCG configuration, whenthe first RRC message does not include the indication and includes thesecond SCG configuration.

In one example, the second SCG configuration comprises a plurality ofconfigurations. In one example, the second SCG configuration includes atleast one first configuration and does not include at least one secondconfiguration in the first SCG configuration. The second SCGconfiguration may not include a release indication indicating release ofthe at least one configuration.

In one example, the second SCG configuration may configure a SN changefrom the second BS to the third BS. In response to the SN change, the UEconnects to the third BS instead of the second BS, while connecting tothe first BS. That is, the UE simultaneously connects to the first BSand the third BS.

In one example, the MCG configuration, the first SCG configurationand/or the second SCG configuration includes at least one of a framestructure configuration, a physical cell identity (PCI), carrierinformation, a temporary identifier (e.g., Cell Radio Network TemporaryIdentifier (C-RNTI)) assigned to the UE, a physical layer configuration(e.g., for physical channel(s), a transmission mode, beamforming, areference signal, a channel state information reporting, a subframeconfiguration, a slot configuration, etc.), a medium access control(MAC) configuration and at least one radio bearer (RB) configuration.

In one example, the at least one RB configuration includes a SRBconfiguration and/or a DRB configuration. Each of the at least one RBconfiguration may include at least one of a RB identity, an EPS beareridentity, a PDU session identity and a radio link control (RLC)configuration. The DRB configuration may configure a SCG part of a DRB(e.g., MCG split bearer), a DRB of a SCG bearer or a DRB of a SCG splitbearer. The RB configuration may or may not include a Packet DataConvergence Protocol (PDCP) configuration. The at least oneconfiguration in the first SCG configuration may includeconfiguration(s) in the first SCG configuration described above.

In one example, the UE releases the first SCG configuration in responseto the indication. The UE communicates with the first BS according tothe MCG configuration and communicates with the third BS according tothe second SCG configuration.

In one example, when the first RRC message does not include theindication and includes the second SCG configuration, the second SCGconfiguration includes change(s) to update one or more configuration(s)in the first SCG configuration. For example, the first SCG configurationincludes a first configuration (which has a first value) and a secondconfiguration. The second SCG configuration may include a second valueof the first configuration, but the second SCG configuration does notinclude the second configuration. Thus, the UE updates the first valueof the first configuration to the second value (i.e., use the secondvalue of the second SCG configuration instead of the first value) andkeeps using the second configuration in the first SCG configuration,when receiving/in response to the second SCG configuration.

In one example, the first SCG configuration includes a firstconfiguration (which has a first value) and a second configuration. Thefirst RRC message includes the second SCG configuration and theindication. The second SCG configuration may include a second value ofthe first configuration but does not include the second configuration.Thus, the UE uses the second value for the first configuration andreleases the second configuration in the first SCG configuration inresponse to the indication. Thus, the UE does not use the secondconfiguration, when receiving/in response to the indication.

In one example, the UE replaces the first SCG configuration with thesecond SCG configuration, when the first RRC message includes theindication and the second SCG configuration. The UE releases the firstSCG configuration and use the second SCG configuration in response tothe indication. In one example, DRB(s) configured by DRBconfiguration(s) in the first SCG configuration may be configured by DRBconfiguration(s) in the second SCG configuration. In one example, the UEreleases the DRB(s) configured by the DRB configuration(s) in the firstSCG configuration and add the DRB(s) configured by the DRB configuration(s) in the second SCG configuration. In one example, the UE reconfiguresor modifies the DRBs according to (e.g., using) the DRB configuration(s)in the second SCG configuration.

In one example, the UE releases the first SCG configuration (i.e.,releases the connection with the second BS), when the first RRC messageincludes the indication but does not include the second SCGconfiguration. The UE is no longer in the DC, and only connects to thefirst BS.

A process 40 in FIG. 4 may be utilized in a network including a first BS(e.g., the BS 102), a second BS (e.g., the BS 104) and a third BS, andincludes the following steps:

Step 400: Start.

Step 402: The first BS communicates with a UE according to (e.g., using)a MCG configuration and the second BS communicates with the UE accordingto a first SCG configuration, when the UE is in the DC with the first BSand the second BS.

Step 404: The first BS transmits a first interface message to the thirdBS to prepare a SN change from the second BS to the third BS, whereinthe first interface message comprises the first SCG configuration.

Step 406: The third BS transmits a second interface message to the firstBS in response to the first interface message, wherein the secondinterface message comprises a second SCG configuration.

Step 408: The first BS transmits a first RRC message to the UE, whereinthe first RRC message comprises the second SCG configuration and anindication indicating release of SCG (e.g., SCG release or SN release).

Step 410: The third BS communicates with the UE according to the secondSCG configuration.

Step 412: End.

According to the process 40, the third BS communicates with the UEaccording to the second SCG configuration instead of the first SCGconfiguration.

In one example, the second interface message includes an informationelement (IE) causing the first BS to include the indication. In oneexample, the third BS determines to include the IE in the secondinterface message, when the third BS cannotrecognize/understand/comprehend a configuration in the first SCGconfiguration. For example, the configuration is added in a version of a3GPP specification later than a version of the 3GPP specificationimplemented by the third BS, such that the third BS does notrecognize/understand the configuration. In one example, the third BSdetermines to include the IE in the second interface messageirrespective of the first SCG configuration since the third BS does notcheck (e.g., read, look at or refer to) the first SCG configuration. Forexample, the IE is a cause IE or a specific IE which indicates therelease of SCG or a full configuration.

In one example, the second interface message does not include the IEcausing the first BS to include the indication. The second interfacemessage itself may indicate or imply the release of SCG (i.e., thesecond SCG configuration has no dependency on the first SCGconfiguration). The first BS knows that the second SCG configuration isa full configuration irrelevant to the first SCG configuration, sincethe third BS is configured to use a full configuration for the secondSCG configuration (i.e., not reusing any configuration in the first SCGconfiguration) instead of using the delta configuration (i.e., reusingone or more configurations in the first SCG configuration). The first BSincludes the indication according to/in response to the second interfacemessage not including the IE.

In one example, the second interface message may not include an IEcausing the first BS not to include the indication. That is, the secondinterface message itself may indicate or imply the first BS does notindicate the release of SCG (i.e., the second SCG configuration hasdependency on the first SCG configuration). The first BS knows that thesecond SCG configuration is a delta configuration dependent on the firstSCG configuration according to the second interface message notincluding the IE. The first BS does not include the indication in thefirst RRC message according to/in response to the second interfacemessage not including the IE.

In another example, the first interface message may include the firstSCG configuration, and the second interface message may include an IEcausing the first BS not to include the indication. The second BScomprehends the first SCG configuration, and generates the second SCGconfiguration according to the first SCG configuration. That is, the IEindicates that the second SCG configuration has dependency on the firstSCG configuration, i.e., the second SCG configuration includes deltaconfiguration(s) from the first SCG configuration. Thus, the first BSknows that the second SCG configuration is a delta configuration on topof the first SCG configuration according to the second interface messageincluding the IE. The first BS does not include the indication in thefirst RRC message according to/in response to the second interfacemessage including the IE. For example, the IE indicates that the deltaconfiguration(s) is used for the second SCG configuration.

In one example, the first interface message includes the MCGconfiguration or apart of the MCG configuration. The first interfacemessage may include the UE's capability. The third BS may determine(content of) the second SCG configuration according to the MCGconfiguration or the part of the MCG configuration.

In one example, the first interface message is a SN Addition Requestmessage, and the second interface message is a SN Addition RequestAcknowledge message. The term of “SN” may be replaced by “secondaryevolved Node-B (SeNB)” or “secondary next generation Node-B (SgNB)”.

In one example, the first BS transmits a third interface message to thesecond BS to release the second BS for the UE, in response to the secondinterface message. In one example, the third interface message is a SNRelease Request message (or called a SN Change Confirm message).

In one example, when the UE receives the first RRC message, the UEreleases (ignores or discards) the first SCG configuration (e.g., thefirst SCG configuration is no longer valid) according to the indication,and uses the second SCG configuration to communicate with the third BS.Thus, the UE is in the DC with the first BS and the third BS in responseto the first RRC message.

The examples described for the process 30 may be applied to the process40, and are not repeated herein.

A process 50 in FIG. 5 may be utilized in a network including a first BS(e.g., the BS 102), a second BS (e.g., the BS 104) and a third BS, andincludes the following steps:

Step 500: Start.

Step 502: The first BS communicates with a UE according to (e.g., using)a MCG configuration and the second BS communicates with the UE accordingto a first SCG configuration, when the UE is in the DC with the first BSand the second BS.

Step 504: The first BS transmits a first interface message to the thirdBS to prepare a SN change from the second BS to the third BS, whereinthe first interface message does not comprise the first SCGconfiguration.

Step 506: The third BS transmits a second interface message to the firstBS in response to the first interface message, wherein the secondinterface message comprises a second SCG configuration.

Step 508: The first BS transmits a first RRC message to the UE, whereinthe first RRC message comprises the second SCG configuration and anindication indicating release of SCG (e.g., SCG release or SN release).

Step 510: The third BS communicates with the UE according to the secondSCG configuration.

Step 512: End.

An advantage of the process 50 is that the first BS does not transmitthe first SCG configuration to the third BS to save resources in aconnection between the first BS and the third BS. The description forthe processes 30-40 may be applied to the process 50. The UEcommunicates with the third BS according to the second SCGconfiguration. Thus, the UE is in the DC with the first BS and the thirdBS in response to the first RRC message.

A process 60 in FIG. 6 may be utilized in a first BS (e.g., the BS 102),a second BS (e.g., the BS 104) and a third BS, and includes thefollowing steps:

Step 600: Start.

Step 602: The first BS communicates with a UE according to (e.g., using)a MCG configuration and the second BS communicates with the UE accordingto a first SCG configuration, when the UE is in the DC with the first BSand the second BS.

Step 604: The first BS transmits a first interface message to the thirdBS to prepare a SN change from the second BS to the third BS.

Step 606: The third BS transmits a second interface message comprisingthe second SCG configuration, to the first BS in response to the firstinterface message, wherein the second SCG configuration comprises a fullconfiguration indication.

Step 608: The first BS transmits a first RRC message to the UE, whereinthe first RRC message comprises the second SCG configuration.

Step 610: The third BS communicates with the UE according to the secondSCG configuration.

Step 612: End.

In one example, the first interface message comprises the first SCGconfiguration. Alternatively, the first interface message does notcomprise the first SCG configuration. An advantage for not including thefirst SCG configuration in the first interface message is that thesecond BS does not need to support the delta configuration.

A process 70 in FIG. 7 may be utilized in a first BS (e.g., the BS 102),a second BS (e.g., the BS 104) and third BS, and includes the followingsteps:

Step 700: Start.

Step 702: The first BS communicates with a UE according to (e.g., using)a MCG configuration and the second BS communicates with the UE accordingto a first SCG configuration, when the UE is in the DC with the first BSand the second BS.

Step 704: The first BS transmits a first interface message to the thirdBS to prepare a SN change from the second BS to the third BS, whereinthe first interface message comprises the first SCG configuration.

Step 706: The third BS transmits a third interface message to reject thefirst interface message when the third BS determines an error in thefirst SCG configuration, wherein the third interface message indicatesthe error in the first SCG configuration.

Step 708: End.

The description for the processes 30-50 may be applied to the processes60-70. The following examples may be applied to the processes 30-70.

In one example, the first BS configures the MCG configuration to the UEvia a RRC connection (e.g., SRB) between the UE and the first BS. In oneexample, the second BS configures the first SCG configuration to the UEvia the first BS and the RRC connection. In one example, the second BSconfigures a part of the first SCG configuration via the first BS andthe RRC connection, and configures the other part of the first SCGconfiguration via a SRB between the UE and the second BS.

In one example, the second BS and the third BS are a same BS. In oneexample of this case, the first BS may transmit the first interfacemessage to request a modification of the first SCG configuration. Thefirst interface message may be a SN Modification Request, and the secondinterface message may be a SN Modification Request Acknowledge. Thefirst BS may transmit the first interface message, when the first BSdetermines to request the modification of the first SCG configuration.In one example, the first BS determines to request the modification ofthe first SCG configuration due to a change of the MCG configuration. Inone example, the first BS determines to request the modification of thefirst SCG configuration due to an addition or release of SCG SCell(s),due to an addition, modification or release of SCG bearer(s), SCG splitbearer(s) and the SCG part of split bearer(s), or due to triggering aPSCell change. In one example, the second BS transmits a fourthinterface message to the first BS to request the first BS to transmitthe first interface message. The fourth interface message may be a SNModification Required message. The second BS may transmit the fourthinterface message, when the second BS detects a system failure or anerror on the UE's transmission.

In one example, the second BS and the third BS may be different BSs.

In one example, the UE transmits the first RRC response message inresponse to the first RRC message.

In one example, the third BS includes the second SCG configuration in asecond RRC message, and includes the second RRC message in the secondinterface message. Then, the first BS may include the second RRC messagein the first RRC message so that the first RRC message includes thesecond SCG configuration. The first RRC response message may include asecond RRC response message responding the second RRC message. The firstBS may transmit the second RRC response message to the third BS. The DRBconfiguration(s) may be included in the first RRC message instead of thesecond SCG configuration or the second RRC message.

In one example, the first RRC message and the first RRC response messagemay be long-term evolution (LTE) RRC messages. For example, the firstRRC message is a LTE RRC Connection Reconfiguration message, and thefirst RRC response message is a LTE RRC Connection Reconfigurationmessage. In one example, the second RRC message and the second RRCresponse message may be new radio (NR) RRC messages. For example, thesecond RRC message is a NR RRC (Connection) Reconfiguration message, andthe second RRC response message is a NR RRC (Connection) Reconfigurationmessage.

In one example, the first RRC message and the first RRC response messageare NR RRC messages. For example, the first RRC message is a NR RRC(Connection) Reconfiguration message, and the first RRC response messagemay be a NR RRC (Connection) Reconfiguration message. In one example,the second RRC message and the second RRC response message are LTE RRCmessages. For example, the second RRC message is a LTE RRC ConnectionReconfiguration message, and the second RRC response message is a LTERRC Connection Reconfiguration message.

In one example, the indication does not impact the MCG configuration.That is, the UE does not release, change or update the MCG configurationin response to the indication.

It should be noted that although the above examples are illustrated toclarify the related operations of corresponding processes. The examplescan be combined and/or modified arbitrarily according to systemrequirements and/or design considerations.

Those skilled in the art should readily make combinations, modificationsand/or alterations on the abovementioned steps, description andexamples. Some steps described above may not necessarily have to be usedin the invention. The abovementioned description, steps and/or processesincluding suggested steps can be realized by means that could behardware, software, firmware (known as a combination of a hardwaredevice and computer instructions and data that reside as read-onlysoftware on the hardware device), an electronic system, or combinationthereof. An example of the means may be the communication device 20. Anyof the processes above may be compiled into the program codes 214. Forthe process involving the first, second and/or third BSs, stepsperformed by the first BS may be compiled into the program codes 214 ofthe first BS, steps performed by the second BS may be compiled into theprogram codes 214 of the second BS and steps performed by the third BSmay be compiled into the program codes 214 of the third BS.

To sum up, the present invention provides a method and related basestation for efficiently handling simultaneous communications.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

What is claimed is:
 1. A first base station (BS), comprising: at leastone storage device; and at least one processing circuit, coupled to theat least one storage device, wherein the at least one storage devicestores, and the at least one processing circuit is configured to executeinstructions of: the first BS receiving a first interface message for acommunication device from a second BS; the first BS transmitting asecond interface message to the second BS in response to the firstinterface message, wherein the second interface message comprises asecondary cell group (SCG) configuration and an information element (IE)causing the first BS to comprise an indication indicating release of SCGin a radio resource control (RRC) message; and the first BS transmittingthe RRC message to the communication device, wherein the RRC messagecomprises the SCG configuration and the indication.
 2. The first BS ofclaim 1, wherein the first BS does not comprise the indication in theRRC message, when the second interface message does not comprise the IE.3. The first BS of claim 1, wherein the first interface message includesa master cell group (MCG) configuration for the communication device ora part of the MCG configuration.
 4. The first BS of claim 1, wherein thefirst interface message comprises another SCG configuration.
 5. A methodfor a first base station (BS), comprising: the first BS receiving afirst interface message for a communication device from a second BS; thefirst BS transmitting a second interface message to the second BS inresponse to the first interface message, wherein the second interfacemessage comprises a secondary cell group (SCG) configuration and aninformation element (IE) causing the first BS to comprise an indicationindicating release of SCG in a radio resource control (RRC) message; andthe first BS transmitting the RRC message to the communication device,wherein the RRC message comprises the SCG configuration and theindication.
 6. The method of claim 5, wherein the first BS does notcomprise the indication in the RRC message, when the second interfacemessage does not comprise the IE.
 7. The method of claim 5, wherein thefirst interface message includes a master cell group (MCG) configurationfor the communication device or a part of the MCG configuration.
 8. Themethod of claim 5, wherein the first interface message comprises anotherSCG configuration.